1. Field of the Invention
The present invention relates to an image-shake correction device configured to shift a lens to correct image shake occurring due to camera shake in an optical apparatus such as a digital camera or a video camera.
2. Description of the Related Art
In connection with the lens barrel of an optical apparatus such as a digital camera, there is a method of correcting image shake occurring due to camera shake or the like during shooting, according to which an image-shake correction lens is shifted along a plane orthogonal to the optical axis.
Japanese Patent Application Laid-Open No. 2002-196382 discusses an image-shake correction device which is composed of a moving coil type shift unit (an image-shake correction device), wherein a magnet is arranged on a base member on a stationary side, and a yoke and a coil are arranged on a shift member holding a lens on a movable side. Three balls are arranged between the base member and the shift member, and the shift member is urged toward the base member to hold the balls therebetween by an attractive force magnetically exerted between the magnet and the yoke (hereinafter referred to as the “magnetic attractive force”). Thus, when the coil is energized, due to the Lorentz force exerted between the coil and the magnet, the shift member is shifted along a plane orthogonal to the optical axis while rolling the balls, thereby effecting image-shake correction.
However, the shift unit discussed in Japanese Patent Application Laid-Open No. 2002-196382 has an issue in that it involves a rotational movement within the optical-axis orthogonal plane of the shift member holding the correction lens. The issue will be discussed below. First, a magnetic attractive force is exerted between the magnet arranged on the base member on the stationary side and the yoke arranged on the shift member. Thus, there exists a magnetic equilibrium position for the magnet and the yoke. When the positional relationship between the magnet and the yoke deviates from the equilibrium position, there is exerted a force restoring them to the former position (hereinafter referred to as the restoring force). Thus, in the shift unit having two driving units respectively driving the shift member in the vertical direction (hereinafter referred to as the pitch direction) and the horizontal direction (hereinafter referred to as the yaw direction) along a plane orthogonal to the optical axis, a positional change in one driving unit generates a restoring force for the other driving unit. For example, when the shift member is moved in the yaw direction, the above-mentioned restoring force is generated for the pitch-direction driving unit, so that there is generated a moment causing the shift member to rotate in the optical-axis-orthogonal plane. Thus, when there is no unit regulating the rotation of the shift member in the optical-axis-orthogonal plane, the shift member is allowed to rotate during the image-shake correction operation. If, as a result of this rotation, the shift member is brought into contact with the stationary member, there may be generated a collision sound or image disturbance. Further, in the case where the components suffer damage from contact, there may be some problem involved in the driving of the shift member thereafter. Thus, in order that the shift member may not come into contact with the peripheral stationary members if it rotates, the distance between them must be large enough. However, this results in an increase in the size of the components, which leads to an increase in the size of the lens barrel.
The shift unit position detection sensor is formed by a combination of a magnet and a magnetic detection element, of alight emitting element and a light receiving element, etc. This position detection sensor is arranged on the assumption that the movement (position) of the correction lens in one of the following directions is to be detected: a yaw direction, which is a horizontal direction, and a pitch direction, which is a vertical direction. Thus, when the shift member rotates greatly, the output characteristics of the position detection sensor undergoes a change, making it impossible to effect accurate position detection; and crosstalk is generated. Further, when the position detection undergoes a change through rotation, it can happen that feedback control of the position of the correction lens is caused, resulting in deterioration in optical performance at the time of image-shake correction.
Here, as discussed in Japanese Patent No. 3229899, it might be possible to regulate the rotation by providing a guide shaft as a unit for reducing the rotation of the shift member in the direction parallel to the plane orthogonal to the optical axis of the shift member. However, this involves provision of a new guide member for regulating the rotation, which may lead to an increase in the size of the apparatus.